For many years, lead has been the standard metal for use in the manufacture of projectiles for gun ammunition. Lead, however, has been found to be toxic and its elimination from gun ammunition projectiles is currently in progress. Because of this long-standing reliance upon lead as the basic metal for the manufacture of gun ammunition projectiles, the art/science of manufacture of gun ammunition projectiles has languished in mediocrity.
Of recent vintage are gun ammunition projectiles formed from metal powders which are compacted into shaped projectiles or which are compacted and thereafter formed into shaped projectiles. There are myriad problems associated with the manufacture of projectiles employing metal powder(s) as the basic material of the projectile. One of these problems relates to the ultimate formation of a pressed powder compact into an aerodynamically acceptable projectile.
Commonly, in the current state of the art, pressed powder compacts, referred to often as “cores”, are loaded into a jacket, such as a cup-shaped copper metal jacket. The core in the jacket is seated against the closed end of the jacket (“core seating”), and the open end of the jacket is formed about the core and shaped to define an aerodynamically desirable leading end of the projectile. For purposes of at least partially closing the open end of the jacket while defining the desired aerodynamic shape on that end of the core/jacket combination which will become the leading end of the projectile when it is fired from a gun, the core is chosen to be shorter in length than the depth of the jacket so that there is a portion of the jacket wall adjacent the open end of the jacket which is void of core material when the seating operation has been completed.
Core seating takes places with the core/jacket combination being held in a die while pressure is applied axially of the core to seat the core within the closed end of the jacket, and in part, to the side wall of the jacket. Thereafter, and usually in a different die, the open end of the jacket is formed inwardly toward the longitudinal centerline of the jacket. This operation may take place in steps, and may involve more than one die, but in the end, the initially open end of the jacket is closed to the extent desired. The initially open end of the jacket may be fully closed or partially closed, in part depending upon the desired terminal ballistics of the projectile.
In certain projectiles, it is desired that the projectile substantially disintegrate upon striking a target, often disintegrating only after limited penetration into a target. Maximum disintegration in these projectiles is desired, including maximum disintegration of the jacket into very small fragments, and disintegration of the powder-based core into particulates which are on the order of the individual particle size of the powder employed in forming the core.
Disintegration of a jacketed projectile, even projectiles formed from lead cores, is known to be enhanced through the use of a “hollow point” at the leading end of the jacketed projectile. However, hollow pointed projectiles suffer from several shortcomings, such as their tendency to misfeed from magazines into the breech of a semi-automatic or automatic weapon; their relatively inefficient aerodynamic effect upon the flight of the projectile to a target; and other ill effects, all of which must be balanced against the requirement that the projectile disintegrate to the fullest extent upon striking a target.